Method of Radio Network Temporary Identifier Allocation in Dual Connectivity

ABSTRACT

A method of RNTI allocation in dual connectivity for a communication device in a wireless communication system is disclosed. The method comprises connecting to a first base station of the wireless communication system, being assigned a first RNTI by the first base station for communication with the first base station, receiving a RRC message for configuring communication with a second base station of the wireless communication from the first base station, wherein the RRC message includes a second RNTI, and the second RNTI is assigned by the second base station and transmitted by the second base station to the first base station, and performing communication with the first base station with the first RNTI and performing communication with the second base station with the second RNTI.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/863,914, filed on Aug. 9, 2013 and entitled “Method and Apparatus forsmall cell enhancement in a wireless communication system”, the contentsof which are incorporated herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method used in a communication devicein a wireless communication system, and more particularly, to a methodof radio network temporary identifier allocation in a wirelesscommunication system.

2. Description of the Prior Art

3GPP in Release 12 proposes dual connectivity for increasing user'sthroughput. Dual connectivity to at least two cells may be served bydifferent evolved NodeBs (eNB), linked with non-ideal backhaul, e.g.,there may be an eNB in charge of a cluster of cells. Therefore, a userequipment (UE) may be served by multiple eNBs when it is in dualconnectivity mode.

The applicant notice a problem associated to C-RNTI allocation in dualconnectivity. In carrier aggregation, the C-RNTI allocation is done by aPCell and a UE is configured a C-RNTI for uplink grant or downlinkassignment. In an example, the UE is connected to an eNB1 with a C-RNTI.The eNB1 may configure the UE to connect to an eNB2 to enable dualconnectivity. However, the C-RNTI in the eNB2 has been assigned toanother UE for data transmission and reception. When the eNB2 schedulesdata transmission on PDCCH with the C-RNTI, the UE and the other UEtransmits data using same frequency resources in a same subframe sinceboth UEs thinks they are scheduled by the eNB2 for uplink datatransmission. Both data transmissions may fail because the eNB2 cannotreceive them due to C-RNTI collision. Even the eNB2 can receive the datatransmission from the UE, the eNB2 may think the data transmission isfrom the other UE and deciphers the data with the other UE's key but theeNB2 cannot receive the data correctly due to using a wrong key todecipher. A similar problem also occurs in downlink communication. TheUE may receive the other UE's data transmitted by the eNB2 because asame C-RNTI used in the UE and the other UE.

SUMMARY OF THE INVENTION

It is there for an objective to provide a method of radio networktemporary identifier allocation in dual connectivity in a wirelesscommunication system to solve the above problem.

The present invention discloses a method of RNTI allocation in dualconnectivity for a communication device in a wireless communicationsystem. The method comprises connecting to a first base station of thewireless communication system, being assigned a first RNTI by the firstbase station for communication with the first base station, receiving aRRC message for configuring communication with a second base station ofthe wireless communication from the first base station, wherein the RRCmessage includes a second RNTI, and the second RNTI is assigned by thesecond base station and transmitted by the second base station to thefirst base station, and performing communication with the second basestation with the second RNTI.

The present invention discloses a method of C-RNTI allocation in dualconnectivity for a communication device in a wireless communicationsystem. The method comprises connecting to a first base station of thewireless communication system, being assigned a first C-RNTI by thefirst base station for communication with the first base station,receiving a RRC message for configuring communication with a second basestation of the wireless communication, performing a non-contention basedrandom access procedure to get a second C-RNTI from the second basestation, and performing communication with the second base station withthe second C-RNTI.

The present invention discloses a method of RNTI allocation in dualconnectivity for a network in a wireless communication system. Themethod comprises receiving a first RNTI request message for requestingan assignment of a first RNTI for a first communication device of thewireless communication system, from a first base station of the wirelesscommunication system, and transmitting a first RNTI response messagecontaining the first RNTI for the first communication device, to thefirst base station, whereby the first base station transmits the firstRNTI assigned by the network to the first communication device.

The present invention discloses a method of C-RNTI allocation in dualconnectivity for a first base station in a wireless communicationsystem. The method comprises connecting to a communication device of thewireless communication system, assigning a first RNTI to thecommunication device for communication with the communication device,and transmitting a radio resource control (RRC) message for configuringthe communication device to communicate with a second base station ofthe wireless communication to the communication device, wherein the RRCmessage includes a second RNTI and the second RNTI is assigned by thesecond base station and transmitted by the second base station to thefirst base station.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication apparatus according toan example of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIGS. 4-6 are schematic diagrams of embodiments according to FIG. 3.

FIG. 7 is a flowchart of a process according to an example of thepresent invention.

FIG. 8 is a schematic diagram of an embodiment according to FIG. 7.

FIGS. 9-11 are schematic diagrams of embodiments according to thepresent invention.

FIG. 12 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of a wirelesscommunication system 10 according to an example of the presentinvention. The wireless communication system 10 is briefly composed of anetwork and a plurality of communication devices. In FIG. 1, the networkand the communication devices are simply utilized for illustrating thestructure of the wireless communication system 10. Practically, thenetwork can be a universal terrestrial radio access network (UTRAN)comprising a plurality of Node-Bs (NBs) in a universal mobiletelecommunications system (UMTS). Alternatively, the network can be anevolved UTRAN (E-UTRAN) comprising a plurality of evolved NBs (eNBs)and/or relays in a long term evolution (LTE) system or a LTE-Advanced(LTE-A) system. The communication device can be a user equipment (UE).

Please refer to FIG. 2, which is a schematic diagram of a communicationapparatus 20 according to an example of the present invention. Thecommunication apparatus 20 can be a communication device or the networkshown in FIG. 1, but is not limited herein. The communication apparatus20 may include a processing means 200 such as a microprocessor orApplication Specific Integrated Circuit (ASIC), a storage unit 210 and acommunication interfacing unit 220. The storage unit 210 may be any datastorage device that can store a program code 214, accessed and executedby the processing means 200. Examples of the storage unit 210 includebut are not limited to a subscriber identity module (SIM), read-onlymemory (ROM), flash memory, random-access memory (RAM), CD-ROM/DVD-ROM,magnetic tape, hard disk and optical data storage device. Thecommunication interfacing unit 220 is preferably a transceiver and isused to transmit and receive signals (e.g., messages or packets)according to processing results of the processing means 200.

Please refer to FIG. 3, which is a flowchart of a process 30 accordingto an example of the present invention. The process 30 is utilized inthe communication device shown in FIG. 1, for RTNI allocation in dualconnectivity in the wireless communication system 10. The process 30 maybe compiled into the program code 314. The process 30 includes thefollowing steps:

Step 300: Start.

Step 302: Connect to a first base station of the wireless communicationsystem.

Step 304: Be assigned a first RNTI by the first base station forcommunication with the first base station.

Step 306: Receive a radio resource control (RRC) message for configuringcommunication with a second base station of the wireless communicationfrom the first base station, wherein the RRC message includes a secondRNTI and the second RNTI is assigned by the second base station.

Step 308: Perform communication with the first base station with thefirst RNTI and perform communication with the second base station withthe second RNTI.

Step 310: End.

According to the process 30, the communication device connects to thefirst base station and uses a first RNTI to communicate with the firstbase station. The first base station may add the second base station inthe communication device configuration for communication, e.g., data orsignaling transmission/reception to/from the communication device viathe second base station, so as to enable dual connectivity. As a result,the first base station sends a RRC message (e.g.RRCConnectionReconfiguration) to configure the communication device tocommunicate with the second base station, wherein the RRC messagecontains the second RNTI assigned by the second base station. Note that,the second base station can generate the RRC message including thesecond RNTI by itself and transmit the RRC message to the first basestation (so that the first station forwards the RRC message to thecommunication device); or, the second base station can transmit thesecond RNTI to the first base station and let the first base station dothe generation of the RRC message. The communication device performscommunication with the first base station with the first RNTI andperforms communication with the second base station with the secondRNTI. Therefore, no RNTI collision will occur in dual connectivity. Notethat, the first and second RNTIs may be C-RNTIs or Semi-PersistentScheduling (SPS) C-RNTIs used for data communication (i.e. datatransmission and/or data reception) with the first base station andsecond base station respectively. The first and second RNTIs may beTransmit Power Control (TPC) RNTIs used for signaling communication(i.e. transmission/reception of TPC commands indicating increasing ordecreasing uplink transmission power) with the first base station andsecond base station respectively.

Take an example based on the process 30. Please refer to FIG. 4, whichis a message sequence chart of a first embodiment according to thepresent invention. First, the UE has a RRC connection to a celll of theeNB1 and has a C-RNTI1 with the eNB1. In order to realize dualconnectivity (namely the UE can communicate with the eNB1 and eNB2simultaneously), the eNB1 transmits a cell addition request to the eNB2,to request for adding a cell2 of the eNB2 for the UE (step 400). TheeNB2 transmits a cell addition response including a C-RNTI2 assigned bythe eNB2 to the eNB1, to respond to the cell addition request (step402). The eNB1 generates and transmits a RRC message including theC-RNTI2 assigned by the eNB2 to the UE after receiving the cell additionresponse (step 404). The UE transmits a RRC response message toacknowledge the reception of the RRC message (step 406). Note that, theRRC message contains at least one of physical cell identity and carrierfrequency to identify the cell2. The physical cell identity and carrierfrequency may be transmitted by the eNB2 to the eNB1 or may be generatedby the eNB1.

After the UE obtains the C-RNTI2 with the eNB2, the UE may perform anon-contention based random access procedure to the eNB2 if thenon-contention based random access procedure is required by the eNB2 foruplink time alignment. In detail, the UE transmits a random accesspreamble in random access channel (RACH) resource location to the eNB2,wherein the random access preamble is assigned by the eNB2 and theassignment is contained in the RRC message (step 404) or in a RApreamble assignment message (step 408), e.g. an PDCCH order, sent by theeNB2. The RACH resource location identifies which subframe(s) is usedfor transmitting the random access preamble and is contained in thepreamble assignment message, or in the RRC message, or in systeminformation broadcasted by the eNB2. The UE receives a random accessresponse from the eNB2. If the random access response includes a randomaccess preamble identifier corresponding to the random access preamble,the UE completes the non-contention based random access procedure. TheUE applies a timing advance command included in the random accessresponse for uplink time alignment with the eNB2. After completing thenon-contention based random access procedure, the UE may simultaneouslymonitor PDCCH/Enhanced PDCCH (EPDCCH) transmitted from the eNB1 withC-RNTI1 and PDCCH/EPDCCH transmitted from the eNB2 with C-RNTI2 (steps414-416). If the UE detects PDCCH/EPDCCH with cyclic redundancy check(CRC) scrambled by C-RNTI2 from the eNB2, the UE decodes thePDCCH/EPDCCH with CRC scrambled by C-RNTI2 and uses downlink assignmentcontained in the PDCCH/EPDCCH for receiving data or uplink grantcontained in the PDCCH/EPDCCH for transmitting data. Hence the UEsimultaneously uses C-RNTI1 for data or signaling transmission/receptionwith the eNB1 and C-RNTI2 for data or signaling transmission/receptionwith the eNB2.

Please refer to FIG. 5, which is a message sequence chart of a secondembodiment according to the present invention. The difference to thefirst embodiment shown in FIG. 4 is that the RRC message including theC-RNTI2 is generated by the eNB2, and is transmitted to the UE via theeNB1.

Alternatively, after the UE obtains the C-RNTI2 with the eNB2, the UEmay perform a contention based random access procedure to the eNB2 ifthe contention based random access procedure is required by the eNB2 foruplink time alignment. Please refer to FIG. 6, which is a messagesequence chart of a third embodiment according to the present invention.The UE transmits a random access preamble in RACH resource location tothe eNB2 (step 608), wherein the random access preamble is selected bythe UE from a set of preambles. The set of preambles and the RACHresource location may be configured in the RRC message or in systeminformation broadcasted by the eNB2. The UE receives a random accessresponse from the eNB2 in response to the random access preamble (step610), wherein the random access response contains an uplink grant and arandom access preamble identifier which corresponds to the selectedrandom access preamble. The UE transmits a scheduled transmission (i.e.MAC PDU) containing the C-RNTI2 according to the uplink grant (step612). In response to the scheduled transmission containing the C-RNTI2,the eNB2 transmits a contention resolution message containing theC-RNTI2 (e.g. PDCCH/EPDCCH with CRC scrambled by C-RNTI2) to the UE.After completing the contention based random access procedure, the UEmay simultaneously monitor PDCCH/EPDCCH transmitted from the eNB1 withC-RNTI1 and PDCCH/EPDCCH transmitted from the eNB2 with C-RNTI2 (steps616-618). If the UE detects PDCCH/EPDCCH with CRC scrambled by C-RNTI2from the eNB2, the UE decodes the PDCCH/EPDCCH with CRC scrambled byC-RNTI2 and uses downlink assignment contained in the PDCCH/EPDCCH forreceiving data or uplink grant contained in the PDCCH/EPDCCH fortransmitting data. Hence the UE simultaneously uses C-RNTI1 for data orsignaling transmission/reception with the eNB1 and C-RNTI2 for data orsignaling transmission/reception with the eNB2.

Note that, if the RRC message further contains a TPC RNTI and uplinktime alignment is required for communication with the eNB2, the UEstarts to apply a TPC command received from the eNB2 in PDCCH/EPDCCHwith CRC scrambled by TPC RNTI after completing a random accessprocedure which is a non-contention based random access procedure or acontention based random access procedure as described above. If the RRCmessage further contains the TPC RNTI and the uplink time alignment forcommunication with eNB2 is not required, the UE starts to apply a TPCcommand received in PDCCH/EPDCCH with CRC scrambled by TPC RNTI afterreceiving the RRC message. Similarly if the RRC message further containsa SPS C-RNTI, after completing a random access procedure, the UE maymonitor PDCCH/EPDCCH transmitted from the eNB2 with the SPS C-RNTI foractivation/deactivation of SPS. In other words, the eNB2 may transmitPDCCH with CRC scrambled with the SPS C-RNTI to activate or deactivateSPS after the random access procedure. If the random access procedure isnot required, the UE starts to monitor PDCCH/EPDCCH with CRC scrambledby the SPS RNTI after receiving the RRC message. The RRC messageindicates the uplink time alignment for communication with eNB2 isrequired or not.

Please refer to FIG. 7, which is a flowchart of a process 70 accordingto an example of the present invention. The process 70 is utilized inthe communication device shown in FIG. 1, for C-RTNI allocation in dualconnectivity in the wireless communication system 10. The process 70 maybe compiled into the program code 314. The process 70 includes thefollowing steps:

Step 700: Start.

Step 702: Connect to a first base station of the wireless communicationsystem.

Step 704: Be assigned a first C-RNTI by the first base station forcommunication with the first base station.

Step 706: Receive a radio resource control (RRC) message for configuringcommunication with a second base station of the wireless communication.

Step 708: Perform a non-contention based random access procedure to geta second C-RNTI from the second base station.

Step 710: Perform communication with the first base station with thefirst C-RNTI and performing communication with the second base stationwith the second C-RNTI.

Step 712: End.

According to the process 70, the communication device connects to thefirst base station and uses a first C-RNTI to communicate with the firstbase station. The first base station may add the second base station inthe communication device configuration for data transmission/receptionto/from the communication device via the second base station, so as toenable dual connectivity. As a result, the first base station sends aRRC message (e.g. RRCConnectionReconfiguration) to configure thecommunication device to communicate with the second base station and theRRC message does not include a second C-RNTI. The UE performs thenon-contention based random access procedure to directly get the secondC-RNTI in a random access response of the non-contention based randomaccess procedure from the second base station, so as to avoid C-RNTIcollision in dual connectivity.

In detail, please refer to FIG. 8, which is a message sequence chart ofa fourth embodiment according to the present invention. First, the UEhas a RRC connection to a celll of the eNB1 and has a C-RNTI1 with theeNB1. In order to realize dual connectivity, the eNB1 transmits a celladdition request to the eNB2, to request for adding a cell2 of the eNB2for the UE (step 800). The eNB2 transmits a cell addition responseincluding RACH configuration for random access procedure for the UE tothe eNB1, to respond to the cell addition request (step 802). The eNB1or the eNB2 generates and transmits a RRC message (e.g.RRCConnectionReconfiguration) for configuring the cell2 of the eNB2 tothe UE after receiving the cell addition response (step 804). Note that,the RRC message contains at least one of physical cell identity andcarrier frequency to identify the cell2. The physical cell identity andcarrier frequency may be transmitted by the eNB2 to the eNB1 or may begenerated by the eNB1. The UE transmits a RRC response message toacknowledge the reception of the RRC message (step 806). In addition,the UE performs a non-contention based random access procedure. The UEtransmits a random access preamble in RACH resource location to theeNB2, wherein the random access preamble is assigned by the second eNBand contained in the RRC message or in a RA preamble assignment message(e.g. PDCCH order) sent by the eNB2 (steps 808-810). The UE receives arandom access response containing a C-RNTI2 from the eNB2 (step 812).After that, the UE may simultaneously monitor PDCCH/EDPCCH transmittedfrom the eNB1 with C-RNTI1 and PDCCH/EPDCCH transmitted from the eNB2with C-RNTI2 (steps 814-816).

On the other hand, please refer to FIG. 9, which is a message sequencechart of a fifth embodiment according to the present invention. Afterthe UE obtains the C-RNTI1 and C-RNTI2 for the eNB1 and eNB2 based onthe abovementioned processes 30 and 70, the UE has datatransmission/reception with the celll of eNB1 by using the C-RNTI1 anddata transmission/reception with the cell2 of eNB2 by using a C-RNTI2.However, the UE may detect radio link failure (RLF) on the cell2 andsuspends or stops transmission and reception on the cell2. The UE maydetect the cell2 again and transmits a random access preamble to thecell2. As a result, the eNB2 transmits the random access response inresponse to the random access preamble. The UE transmits a scheduledtransmission containing the C-RNTI2 according to an uplink grantcontained in the received random access response. The UE receives acontention resolution message containing the C-RNTI2 after transmittingthe scheduled transmission. After the UE completes the random accessprocedure, the UE considers the radio link with the cell2 is recoveredand resumes transmission and reception on the cell2.

Note that, if the RRC message further contains a TPC RNTI, the UE startsto apply a TPC command received from the eNB2 in PDCCH/EPDCCH with CRCscrambled by TPC RNTI after completing a random access procedure whichis a non-contention based random access procedure or a contention basedrandom access procedure as described above. Similarly if the RRC messagefurther contains a SPS C-RNTI, after completing a random accessprocedure, the UE may monitor PDCCH/EPDCCH transmitted from the eNB2with the SPS C-RNTI for activation/deactivation of SPS. In other words,the eNB2 may transmit PDCCH with CRC scrambled with the SPS C-RNTI toactivate or deactivate SPS after the random access procedure. The RRCmessage indicates the uplink time alignment for communication with eNB2is required or not.

In another embodiment, after the UE detects the RLF, the UE starts atimer; after the timer expires, the UE releases a configuration of thecell2 of the eNB2 (e.g. the C-RNTI2). On the other hand, the UE stopsthe timer when the UE considers the radio link is recovered or receivesa RRC message from the eNB1, wherein the RRC message indicates the UE torelease the configuration of the cell2 of the eNB2. In addition, the RRCmessage may contain at least one of (physical) cell identity and carrierfrequency to identify the cell2 of the eNB2. Alternatively the RRCmessage may contain an index to identify the cell2. The indexcorresponds to the cell2 and was assigned in a RRC message configuringcommunication with the cell2.

In another embodiment, as shown in FIG. 10, after the UE detects theRLF, the UE transmits a first RRC message indicating the RLF to the eNB2via the eNB1. After the eNB2 receives the first RRC message, the eNB2sends a remove cell request or a remove cell indication to the eNB1. TheeNB1 or the eNB2 transmits a second RRC message in response to the firstRRC message to indicate the UE to release the configuration of the cell2of the eNB2.

In another embodiment, as shown in FIG. 11, after the UE detects theRLF, the UE transmits a first RRC message to the eNB1. The eNB 1 thensends a remove cell request or a remove cell indication to the eNB2. TheeNB1 or the eNB2 (via the eNB1) transmits a second RRC message inresponse to the first RRC message to indicate the UE to release theconfiguration of the cell2 of the eNB2.

Please refer to FIG. 12, which is a flowchart of a process 120 accordingto an example of the present invention. The process 120 is utilized inthe network shown in FIG. 1, for RTNI allocation in dual connectivity inthe wireless communication system 10. The process 120 maybe compiledinto the program code 314. The process 120 includes the following steps:

Step 1200: Start.

Step 1202: Receive a first RNTI request message for requesting anassignment of a RNTI for a first communication device of the wirelesscommunication system, from a first base station of the wirelesscommunication system.

Step 1204: Transmit a first RNTI response message containing a firstRNTI for the first communication device, to the first base station,thereby the first base station transmits the first RNTI assigned by thenetwork to the first communication device.

Step 1206: End.

According to the process 120, a network node is responsible for RNTIallocation request by other base stations. In an example, when an eNB1needs to allocate a RNTI to a UE1, the eNB1 sends a RNTI request to thenetwork node and the network node responds with a RNTI responsecontaining a first RNTI. Then, the eNB1 transmits the first RNTI to theUE1. In addition, when an eNB2 needs to allocate a RNTI to a UE2, theeNB2 also sends a RNTI request to the network node and the network noderesponds with a RNTI response containing the second RNTI. The eNB2transmits the second RNTI to the UE2, wherein the first RNTI and thesecond RNTI shall be different. Note that, the first and second RNTIsmay be C-RNTIs or Semi-Persistent Scheduling (SPS) C-RNTIs used for datacommunication (i.e. data transmission and/or data reception) with theeNB1 and eNB2 respectively. The first and second RNTIs may be TransmitPower Control (TPC) RNTIs used for signaling communication (i.e.transmission/reception of TPC commands indicating increasing ordecreasing uplink transmission power) with the eNB1 and eNB2respectively.

According to the above, when a UE communicating with the eNB1 using afirst RNTI assigned by the eNB1 is configured to further communicatewith the eNB2, the eNB2 does not need to assign a second RNTI for a UE.In other words, the UE1 is configured with a single RNTI for bothcommunication with the eNB1 and communication with the eNB2 because noUEs use a same RNTI to communicate with a same eNB. Since the RNTIallocation is centralized for the eNB1 and eNB2, the RNTI collision intwo UEs is resolved. The network node does not allocate the same RNTI totwo UEs if the two UEs perform data transmission/reception in a sameeNB.

In conclusion, the UE obtains a RNTI of a newly added eNB with a RRCmessage for configuring the newly added eNB to the UE, from a connectedeNB, or with a random access response of a non-contention based randomaccess procedure, so as to avoid RNTI collision in dual connectivity.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method of radio network temporary identifier(RNTI) allocation in dual connectivity for a communication device in awireless communication system, comprising: connecting to a first basestation of the wireless communication system; being assigned a firstRNTI by the first base station for communication with the first basestation; receiving a radio resource control (RRC) message including asecond RNTI for configuring communication with a second base station ofthe wireless communication from the first base station, wherein thesecond RNTI is assigned by the second base station; and performingcommunication with the second base station with the second RNTI.
 2. Themethod of claim 1, wherein the RRC message is generated by the firstbase station or the RRC message is generated by the second base stationand transmitted from the second base station to the first station. 3.The method of claim 1, further comprising: transmits a random accesspreamble in a random access channel (RACH) resource location to thesecond base station, wherein the random access preamble is selected bythe communication device from a set of preambles broadcasted by thesecond base station in system information or configured in the RRCmessage, and the RACH resource location is configured in the RRC messageor broadcasted by the second base station in the system information;receiving a random access response from the second base station inresponse to the random access preamble, wherein the random accessresponse contains a random access preamble identifier corresponding tothe random access preamble, a timing advance command and an uplinkgrant; applying the timing advance command for uplink time alignmentwith the second base station; transmitting a scheduled transmissioncontaining the second RNTI to the second base station according to theuplink grant; and receiving a contention resolution message containingthe second RNTI from the second base station.
 4. The method of claim 1,further comprising: transmits a random access preamble in a randomaccess channel (RACH) resource location to the second base station,wherein the random access preamble is assigned by the second basestation and contained in the RRC message or in a random access preambleassignment message transmitted by the second base station, and the RACHresource location is configured in the RRC message or broadcasted by thesecond base station in the system information; receiving a random accessresponse from the second base station in response to the random accesspreamble, wherein the random access response contains a random accesspreamble identifier corresponding to the random access preamble, atiming advance command and an uplink grant; and applying the timingadvance command for uplink time alignment with the second base station.5. The method of claim 1, further comprising: transmitting a secondrandom access preamble to the second base station after a radio linkfailure is detected in communication with the second base station;receiving a second random access response including an uplink grant inresponse to the second random access preamble, from the second basestation; transmitting a second schedule transmission containing thesecond RNTI to the second base station according to the uplink grant;receiving a second contention resolution message containing the secondRNTI from the second base station; and considering the radio link withthe second base station is recovered.
 6. The method of claim 5, furthercomprising: starting a timer when detecting the radio link failure incommunication with the second base station; and stopping the timer whenthe communication device considers the radio link is recovered or whenthe communication device receives a second RRC message indicating thecommunication device to release a configuration associated to the secondbase station and stored in the communication device, from the first basestation; and releasing the configuration when the timer expires.
 7. Themethod of claim 6, wherein the second RRC message contains at least oneof an identity and carrier frequency to identify the second basestation.
 8. The method of claim 1, further comprising: transmitting athird RRC message indicating a radio link failure to the second basestation via the first base station, after the radio link failure isdetected in communication with the second base station; and receiving afourth RRC message in response to the third RRC message to indicate thecommunication device to release a configuration associated to the secondbase station, from the second base station.
 9. The method of claim 1,further comprising: transmitting a fifth RRC message indicating a radiolink failure to the first base station, after the radio link failure isdetected in communication with the second base station, thereby thefirst base station transmits a cell remove request message to the secondbase station when receiving the fifth RRC message; and receiving a sixthRRC message in response to the fifth RRC message to indicate thecommunication device to release a configuration associated to the secondbase station, from the first base station.
 10. A method of cell radionetwork temporary identifier (C-RNTI) allocation in dual connectivityfor a communication device in a wireless communication system,comprising: connecting to a first base station of the wirelesscommunication system; being assigned a first C-RNTI by the first basestation for communication with the first base station; receiving a radioresource control (RRC) message for configuring communication with asecond base station of the wireless communication; performing anon-contention based random access procedure to get a second C-RNTI fromthe second base station; and performing communication with the secondbase station with the second C-RNTI.
 11. The method of claim 10, whereinperforming the non-contention based random access procedure to get thesecond C-RNTI from the second base station comprises: transmitting arandom access preamble in a random access channel (RACH) resourcelocation to the second base station, wherein the random access preambleis assigned by the second base station and configured in the RRC messageor in a random access preamble assignment message sent by the secondbase station, and the RACH resource location is configured in the RRCmessage or broadcasted by the second base station in system information;and receiving a random access response containing the second C-RNTI fromthe second base station.
 12. The method of claim 10, wherein the RRCmessage contains at least one of an identity and carrier frequency toidentify the second base station.
 13. The method of claim 10, furthercomprising: performing a second random access procedure to the secondbase station after a radio link failure is detected in communicationwith the second base station, wherein the second random access procedurecomprises: transmitting a second random access preamble to the secondbase station; receiving a second random access response including anuplink grant, from the second base station; transmitting a secondschedule transmission containing the second C-RNTI to the second basestation according to the uplink grant; receiving a second contentionresolution message containing the second C-RNTI from the second basestation; and considering the radio link with the second base station isrecovered.
 14. The method of claim 13, further comprising: starting atimer when detecting the radio link failure in communication with thesecond base station; and stopping the timer when the communicationdevice considers the radio link is recovered or when the communicationdevice receives a second RRC message indicating the communication deviceto release a configuration associated to the second base station andstored in the communication device, from the first base station; andreleasing the configuration when the timer expires.
 15. The method ofclaim 14, wherein the second RRC message contains at least one of anidentity and carrier frequency to identify the second base station. 16.The method of claim 10, further comprising: transmitting a third RRCmessage indicating a radio link failure to the second base station viathe first base station, after the radio link failure is detected incommunication with the second base station; and receiving a fourth RRCmessage in response to the third RRC message to indicate thecommunication device to release a configuration associated to the secondbase station, from the second base station.
 17. The method of claim 10,further comprising: transmitting a fifth RRC message indicating a radiolink failure to the first base station, after the radio link failure isdetected in communication with the second base station, thereby thefirst base station transmits a cell remove request message to the secondbase station when receiving the fifth RRC message; and receiving a sixthRRC message in response to the fifth RRC message to indicate thecommunication device to release a configuration associated to the secondbase station, from the first base station.
 18. A method of radio networktemporary identifier (RNTI) allocation in dual connectivity for anetwork in a wireless communication system, comprising: receiving afirst RNTI request message for requesting an assignment of a RNTI for afirst communication device of the wireless communication system, from afirst base station of the wireless communication system; andtransmitting a first RNTI response message containing a first RNTI forthe first communication device, to the first base station, whereby thefirst base station transmits the first RNTI assigned by the network tothe first communication device.
 19. The method of claim 18, furthercomprising receiving a second RNTI request message for requesting anassignment of a RNTI for a second communication device of the wirelesscommunication system, from a second base station of the wirelesscommunication system; and transmitting a second RNTI response messagecontaining a second RNTI for the second communication device, to thesecond base station, whereby the second base station transmits thesecond RNTI assigned by the network to the second communication device;wherein the second RNTI assigned by the network is the same as the firstRNTI if the first and the second base stations communicate with the samecommunication device at the same time.
 20. A method of radio networktemporary identifier (RNTI) allocation in dual connectivity for a firstbase station in a wireless communication system, comprising: connectingto a communication device of the wireless communication system;assigning a first RNTI to the communication device for communicationwith the communication device; transmitting a radio resource control(RRC) message for configuring the communication device to communicatewith a second base station of the wireless communication to thecommunication device, wherein the RRC message includes a second RNTI,and the second RNTI is assigned by the second base station andtransmitted by the second base station to the first base station.